The Turkish government has given its formal approval for the United States to use the Incirlik air base in southern Turkey for raids against Islamic State (IS) militants in Syria, a foreign ministry official said Wednesday.

"The cabinet has signed the decree," the official told AFP, without specifying when the authorisation was given. "The (Incirlik) air base can be used (by the US against IS) anytime."

The accord came after months of tough negotiations between the two NATO allies that saw Washington grow increasingly frustrated over Turkey's reluctance to play a robust role in the international coalition against jihadists.

The decree signed by the cabinet authorises the implementation of an agreement between Turkey and the United States on the base that was thrashed out during a visit to Ankara by US presidential envoy John Allen earlier this month.

The cabinet has agreed to "implement elements agreed between Turkey and the United States," said the official. "The basis is there for the use of the facility," the official added.

The United States has long pushed for the use of the base in the campaign against IS jihadists in Syria due its location relatively close to Syria just outside the Turkish city of Adana.

Turkey's failure to let US planes use the base for raids against IS in Syria had caused severe irritation in Washington. But Ankara is now hardening its line against the group.

Turkey blamed deadly suicide bombing in a Turkish border town on IS and on Friday, Turkish warplanes for the first time bombed the IS targets in Syria.

The agreement comes as Turkey also takes military action against Kurdish militants in northern Iraq, a move some analysts see as tacitly approved by Washington in exchange for the Incirlik deal.